The present invention relates to gas turbine engines and, more particularly, to a seal used in gas turbine engines, gas turbine engine starters, and auxiliary power units, that provides increased wear life compared to presently known seals.
Many relatively large turbine engines, including turbofan jet engines, may use an air turbine starter (ATS) to initiate their rotation. The ATS is mounted by the jet engine, much as a starter for an automobile is located by the automobile""s engine. The ATS may be coupled to a high pressure fluid source, such as compressed air, which impinges upon the turbine wheel in the ATS causing it to rotate at a relatively high rate of speed. The ATS includes an output shaft that is coupled, perhaps via one or more gears, to the jet engine. The output shaft rotation in turn causes the jet engine to begin rotating. The applicant for the present invention, Honeywell International, Inc., has for years successfully designed, developed and manufactured ATSs.
The ATS turbine wheel output shaft may be rotationally mounted within a housing using one or more bearing assemblies. The bearing assemblies, as well as the above noted gears, may be supplied with a lubricant, such as oil. Thus, the ATS may be mounted within a housing that is divided into at least two sections, the turbine section and the output section. The turbine section houses the turbine wheel and includes one or more passages through which the high pressure fluid source passes and impinges upon the turbine wheel, causing the turbine wheel to rotate. The output section may house the turbine wheel output shaft, the gears, the bearing assemblies, and various other mechanical devices that utilize a lubricant. A seal assembly may be provided between the turbine section and output section of the ATS to substantially inhibit the lubricant used in output section from leaking out of the output section into the turbine section.
The seal assembly may be a face seal that includes a rotor, a seal ring, and a seal case. The rotor is mounted on the turbine wheel output shaft and, thus, rotates with the output shaft, and has an axially facing flange that extends radially away from shaft. The seal case is mounted to the ATS housing in the turbine section and surrounds the turbine wheel output shaft. The seal ring is housed within the seal case and sealingly engages the axially facing flange of the rotor. To inhibit the seal ring from rotating with the rotor, the seal ring may include one or more anti-rotation notches, and the seal case may include one or more anti-rotation tabs, which are inserted into the ant-rotation notches.
The above-described anti-rotation tabs on the seal case may, under certain circumstances, wear into the sides of anti-rotation notches in the stator ring and form a wear groove. As shown more clearly in FIG. 11, this wear groove 1102 may eventually form a circumferential face 1104 in the side of the stator ring anti-rotation notch 1106, forming an edge or comer 1108 between the wear groove circumferential face 1104 and the circumferential end face 1112 of the stator ring anti-rotation notch 1106. The stator case anti-rotation tab 1114 may contact the edge 1108 formed in the anti-rotation notch 1106, which can lock the seal ring 1116 in the axial direction, and result in leakage between the turbine section and the outside environment. This leakage can result in sufficient loss of lubrication to the bearings, gears, and other lubricated components in the air turbine starter gearbox to cause damage to these components. It should be appreciated that ATS""s with the above design are nonetheless safe for their intended use.
Hence, there is a need for a seal assembly that reduces the likelihood of lock-up between the seal anti-rotation notches and seal case anti-rotation tabs due to wear groove formation in the anti-rotation notches, thereby reducing the likelihood of loss of lubrication to rotating components within the starter gearbox. The present invention addresses this need.
The present invention provides a seal assembly that reduces the likelihood of lock-up between the anti-rotation notches formed in the seal and the anti-rotation tabs formed in the seal case.
In one embodiment of the present invention, and by way of example only, an air turbine starter includes a housing, a turbine wheel, a seal rotor, a seal case, at least one anti-rotation tab, a seal, and at least one anti-rotation notch. The housing has a fluid inlet port, a fluid outlet port, and a fluid flow passage extending therebetween. The turbine wheel has a turbine shaft rotationally mounted within the housing, and at least two turbine blades extending radially into the fluid flow passage. The seal rotor is mounted on the turbine shaft and has an axially facing flange extending radially away from the turbine shaft. The seal case is mounted on the housing and surrounds the turbine shaft, and has an inner surface and an outer surface. Each anti-rotation tab extends from the seal case inner surface. The seal is mounted within the seal case and has a first face, a second face, and an outer peripheral surface extending therebetween. The first face sealingly engages the axially facing flange. Each anti-rotation notch is formed in the seal outer peripheral surface and receives an anti-rotation tab therein. Each anti-rotation notch has at least two side surfaces and an end surface, with the end surface having at least first and second arcuate portions formed substantially symmetric about an axis that intersects the anti-rotation notch.
In another exemplary embodiment, a seal assembly includes a seal case, at least one anti-rotation tab, a seal, and at least one anti-rotation notch. The seal case has an inner surface and an outer surface. Each anti-rotation tab extends from the seal case inner surface. The seal is mounted within the seal case and has a first face, a second face, and an outer peripheral surface extending therebetween. Each anti-rotation notch is formed in the seal outer peripheral surface and receives an anti-rotation tab therein. Each anti-rotation notch has at least two side surfaces and an end surface, with the end surface having at least first and second arcuate portions formed substantially symmetric about an axis that intersects the anti-rotation notch.
In yet another exemplary embodiment, in an air turbine starter including a housing, a turbine wheel having a turbine shaft rotationally mounted within the housing, a seal rotor mounted on the turbine shaft, and a stator seal assembly mounted to the housing and surrounding the shaft and having at least a portion thereof sealingly engaging a face of the seal rotor, a method of modifying the air turbine starter includes removing the stator seal assembly from the turbine housing, and mounting a new stator seal assembly on the turbine housing. The new stator seal assembly includes a seal case, at least one anti-rotation tab, a seal, and at least one anti-rotation notch. The seal case has an inner surface and an outer surface. Each anti-rotation tab extends from the seal case inner surface. The seal is mounted within the seal case and has a first face, a second face, and an outer peripheral surface extending therebetween. Each anti-rotation notch is formed in the seal outer peripheral surface and receives an anti-rotation tab therein. Each anti-rotation notch has at least two side surfaces and an end surface, with the end surface having at least first and second arcuate portions formed substantially symmetric about an axis that intersects the anti-rotation notch.
In other aspects of the present invention, one or more of the above elements can be used in a gas turbine engine.